The invention relates to a pinion starter, and in particular to a pinion starter, drive a pinion starter having such a drive, and to a method for manufacturing such a pinion starter drive.
Such pinion starter drives and pinion starters are known from the prior art and are frequently referred to in motor vehicles as starters (Europa Lehrmittel, Fachkunde Kraftfahrzeugtechnik [Field of Motor Vehicle Technology], 2009; pp 580 et seq).
In motor vehicles, not only drive components are subject to regulations relating to acoustics. Since noise is often felt to be disruptive by vehicle occupants even during the starting process of the internal combustion engine, the so-called pinion starter, as is used to start the internal combustion engine in many motor vehicles, is also subject to such requirements. The invention will be described below with reference to such a pinion starter in a passenger motor vehicle, but this is not to be understood as a restriction of the invention.
In the case of a pinion starter, drive power is transmitted from an electric motor to the internal combustion engine via the pinion starter drive which is preferably embodied as a spur gear unit with two axis-parallel transmission shafts, in order to accelerate said internal combustion engine to the starting rotational speed and to transfer it into the combustion mode.
More preferably, the pinion starter drive is therefore arranged as a spur gear unit with two externally toothed spur gears which are arranged on these transmission shafts, and are designed to mesh with one another in order to transmit power. In this context, cost-effective gear wheels in which the actual toothing geometry is within a broad tolerance range with respect to a target toothing geometry are frequently used for the pinion starter drive, in particular owing to the short running times. These deviations of the toothing geometry can give rise to increased emission of sound during the operation of the pinion starter drive, that is to say during the rolling of the drive pinion on the starter gear. An object of the invention is to make available a pinion starter drive which has a simple design and reduced emission of sound.
This object is achieved by means of a pinion starter drive as claimed in patent claim 1, and a pinion starter having such a drive.
According to the invention, a pinion starter drive is to be understood as being a gear drive device which has a drive pinion and a starter gear, wherein these gear wheels are rotatably mounted on preferably axis-parallel axes and also preferably embodied as externally toothed spur gears. In this context, the spur gear can be driven by the drive pinion, at least during the starting process.
The starter gear and the drive pinion preferably have a normal modulus which is greater than 1.75 mm and preferably greater than 2 mm and particularly preferably greater than or equal to 2.1 mm and the normal modulus is also less than 3.5 mm, preferably less than 2.75 mm and particularly preferably less than or equal to 2.55 mm. The normal modulus of these gear wheels is preferably 2.11 mm or preferably 2.54 mm.
The gearwheels also preferably have an evolvent toothing system for transmitting movement. The gearwheels are preferably manufactured with a toothing quality according to DIN 3962 (08/1978) Quality Class 8 or worse, preferably 10 or worse and particularly preferably Quality Class 11 or worse, or according to the corresponding quality levels according to ISO 1328 or AGMA 2000, AGMA 2015 or BS 436. Where reference is made to DIN 3962, reference is made to DIN 3962, parts 1 to 3 in the version of August 1978.
In order to start the internal combustion engine, the drive pinion is mounted so as to be rotatable about a drive axis and the starter gear is mounted so as to be rotatable about a starter axis; these axes are preferably oriented axis-parallel with respect to one another. According to the invention, a drive reference plane is to be understood as a virtual plane which is oriented orthogonally with respect to the drive axis. At least one tooth of the drive pinion also preferably has an actual drive profile in the drive reference plane. According to the invention, the actual drive profile is understood to be the sectional line of a surface region of the drive pinion with the drive reference plane, wherein this surface region is configured to make contact with the starter gear (active tooth edge).
According to the invention, a starter reference plane is understood to be a virtual plane which is oriented orthogonally with respect to the starter axis. At least one tooth of the starter gear also preferably has an actual starter profile in the starter reference plane. According to the invention, the actual starter profile is to be understood as being the sectional line of a surface region of the starter gear with the starter reference plane, which region is configured to make contact with the drive pinion (active tooth edge).
The drive reference plane and the starter reference plane preferably coincide geometrically in a common virtual plane. In particular, the radially outer half of these actual profiles (actual drive profile, actual starter profile) are embodied as a tooth tip region, and the radially inner half as a tooth base region.
In particular, a target profile (target drive profile, target starter profile), with which the respective actual profile (actual drive profile, actual starter profile), can be compared, can be predefined in each of these reference planes (starter reference plane, drive reference plane). This target profile also preferably corresponds to an idealized toothing profile, such as would be produced in the case of idealized manufacture without any deviation and, in particular, without any profile correction. Gearwheels with an evolvent toothing are preferably used for the pinion starter drive.
Such a target (evolvent) profile can clearly be generated by a thread structure. For this purpose, a thread, at whose end there is a pen, is unwound from a (base circle) cylinder. If the thread is held tautly stretched here (so that it forms a straight line), the pin describes a circular evolvent. This means that all the points of a straight line (referred to as the generatrices) which roll on a circle describe circular evolvents (Niemann, Winter, Maschinenelemente [Machine Elements], Volume II, 1989).
In this context, according to the invention the target profile (target drive profile, target starter profile) is to be understood, in particular, as an evolvent profile of the type described above.
In reality, the tooth edges are usually generated with a tool which has or models the profile of a face toothing arrangement, in particular of a toothed rack with straight-edged, trapezoidal teeth. In this context, this tool rolls with its rolling straight lines on a manufacturing rolling circuit of the gearwheel to be generated, and this can be, in particular, the base circle (generally the pitch circle) of the gearwheel to be manufactured. The actual profile (actual drive profile, actual starter profile) is here the result of this manufacturing process and differs from the target profile (target drive profile, target starter profile) owing to unavoidable manufacturing influences.
In particular, at least the actual drive profile or the actual starter profile or both therefore deviate at least in certain sections from the respective target profile (target drive profile, target starter profile). The actual drive profile preferably deviates from the target drive profile of the drive pinion in the tooth base region, at least in certain sections, by a discrete value FdriveF, and preferably toward the interior of the tooth of the drive pinion (retracted portion of the tooth base). The actual starter profile preferably deviates from the target starter profile of the starter gear in the tooth tip region, at least in certain sections, by a discrete value FstarterK, preferably toward the interior of the tooth of the starter gear (retracted portion of the tooth tip). Both actual profiles also preferably deviate from the respective target profiles in this way. The sum of at least two discrete values of the deviations (FdriveF, FstarterK) in the tooth base region of the drive pinion, or in the tooth tip region of the starter gear (S=FdriveF+FstarterK) is preferably less than zero, wherein deviations of the actual profile with respect to the target profile in the direction of the interior of the tooth each have a negative sign, considered figuratively a portion where material is removed. A pinion starter drive therefore preferably has a gearwheel pair composed of the drive pinion and starter gear, with toothing arrangements with either a retracted portion of the tooth base on the drive pinion or a retracted portion of the tooth tip on the starter gear, or with both.
The values for FdriveF and FstarterK are also preferably each determined on the drive pinion or on the starter gear, respectively, in such a way that the points at which the deviations are determined are in contact when the gearwheels roll, that is to say are located on what is referred to as the engagement line of the toothing arrangement.
At least one of these deviations FdriveF or FstarterK or both are preferably selected from a range in which it is true that the deviation is preferably greater than 15 μm, preferably greater than 20 μm and particularly preferably greater than 30 μm, and the deviation is also preferably less than 80 μm, preferably less than 60 μm and particularly preferably less than, or at least essentially, 40 μm.
Such a configuration of the toothing arrangements makes it possible, in particular, to prevent early tooth engagement, and furthermore it is therefore made possible, in particular, to reduce the portion of the bracing or pushing and sliding of the transmission of movement and as a result to decrease the emission noise during the transmission of movement.
At least the actual drive profile or the actual starter profile or both preferably deviate from the target drive profile and from the target starter profile, at least in certain sections, by more than 9 μm, preferably, by more than 10 μm and particularly preferably by more than 12 μm, and also by less than 80 μm, preferably by less than 55 μm and particularly preferably by less than 30 μm and quite particularly preferably by less than 20 μm. This deviation is preferably to be understood as corresponding to the deviation fHα according to the present specialist knowledge and, in particular, according to DIN 3962.
These gearwheels (drive pinion, starter gear) of a pinion starter drive preferably have a quality level according to DIN 3962 of 8 or worse. These quality levels are, in particular, outside the minimum accuracy level which is necessary according to specialist knowledge (Niemann, Winter, Maschinenelemente [Machine Elements], Volume II, 1989) for correction of the toothing arrangement, in particular a retracted portion of the tooth tip, retracted portion of the tooth base, so that these corrections of the toothing arrangement have a positive effect.
In one preferred embodiment, the values FdriveF or FstarterK or both each comprise an arithmetic mean value formation from at least 2 discrete deviations of the actual drive profile from the target drive profile, in particular in the tooth base region, or of the actual starter profile from the target starter profile, in particular in the tooth tip region. In particular, forming mean values permits better detection of the actual deviations of the respective actual profiles from the target profile.
In one preferred embodiment, the absolute value of at least one of the deviations FdriveF is selected from a range which is greater than 2 μm, preferably greater than 3 μm, preferably greater than 4 μm and particularly preferably greater than or equal to 5 μm and also less than 60 μm, preferably less than 45 μm, preferably less than 35 μm and particularly preferably less than or equal to 25 μm. Investigations have shown that, in particular, toothing corrections on the basis of the proposed value range are particularly effective.
In one preferred embodiment of the invention, the absolute value of at least one of the deviations FstarterK is selected from a range which is greater than 2 μm, preferably greater than 3 μm, preferably greater than 4 μm and particularly preferably greater than or equal to 5 μm and also this range is less than 60 μm, preferably less than 45 μm, preferably less than 35 μm and particularly preferably this range is less than 25 μm. Investigations have shown that, in particular, toothing corrections on the basis of the proposed value range are particularly effective.
In one preferred embodiment, the deviation FdriveF (deviation, drive pinion, tooth base region) comprises an, in particular arithmetic, mean value from a multiplicity of discrete deviations (FdriveF) and corresponds in absolute value, at least essentially, to 20 μm. The deviation FstarterK (deviation, starter gear tooth tip region) also preferably comprises an, in particular arithmetic, mean value from a multiplicity of discrete deviations (FstarterK) and corresponds in absolute value, at least essentially, to 20 μm.
In one preferred embodiment, a multiplicity of teeth of the drive pinion or of the starter gear or of both are configured according to at least one of the previously mentioned rules, with the result that teeth are in contact either with a retracted portion of a tooth tip or with a retracted portion of a tooth base or with both, and therefore the condition S for the sum of the deviations is met.
A pinion starter is to be understood according to the invention as being a starter device for an internal combustion engine in a motor vehicle. In this context, such a pinion starter preferably has a pinion starter drive according to the invention and an electric motor for driving the internal combustion engine via the pinion starter drive during the starting process. Furthermore, such a pinion starter has a shifting device for shifting the drive pinion, in particular in the direction of the drive axis. In this context, the shifting device is configured, in particular, in such a way that the drive pinion is mounted in such a way that it can be engaged with the starter gear, referred to as meshing of the drive pinion in the starter gear, during the starting process. The drive pinion can also preferably be disengaged by the shifting device after the starting process. Such shifting devices are known from the prior art. In particular, using a starter pinion which is configured in such a way, it is possible to reduce emission of noise during the starting process of the internal combustion engine, and therefore to increase the comfort for the motor vehicle.
A method for manufacturing a pinion starter drive makes it possible to select a pinion starter drive according to the invention from a multiplicity of drive pinions and a multiplicity of starter gears. Preferably, when there is a multiplicity of drive pinions at least one deviation FdriveF is detected in each case. When there is a multiplicity of starter gears, in each case at least one deviation FstarterK is also preferably detected. This detection of the deviations is preferably carried out by means of a measuring process. A gearwheel pair is preferably selected from the multiplicity of drive pinions and the multiplicity of starter gears in such a way that for the sum S of the deviation FdriveF and the deviation FstarterK it is true that S is less than 0. In particular, a gearwheel pair which is selected in such a way has particularly low emissions of noise during the starting process.
In particular, a pinion starter drive according to the invention can be implemented with helical gearwheels (drive pinion, starter gear) or preferably with straight-toothed gearwheels.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.